770 CALKINS. 



DESCRIPTION OF PLATE XLI. 



Fig. 13. The nucleus and amphiaster during metaphase. The latter lies in 

 the secondary axis. Central-spindle, nuclear plate, and asters are shown. Mantle- 

 fibers not represented. 



Fig. 14. Metaphase showing position of the nuclear plate and the dumb-bell- 

 shaped amphiaster. 



Fig. 15. Metaphase stage viewed from the opposite side, i.e., the side away 

 from the central-spindle. The chromosomes are seen in optical section. 



Fig. 16. Late anaphase seen from side opposite the spindle. The chromo- 

 somes are completely separated and show secondary thickenings at the ends 

 towards the spheres. The nucleus has elongated in the direction of the secondary 

 axis. 



Fig. 17. Late anaphase showing the position of the central-spindle; the 

 chromosomes are completely separated. 



Fig. 18. Telophase showing the formation of the secondary nuclear plates 

 and just previous to the division of the daughter-spheres. The plane of the next 

 division is therefore clearly indicated. 



Fig. 19. Late anaphase showing final division of the chromosomes. The 

 nucleus and the central-spindle were curved so that only one pole (the upper) was 

 sectioned. 



Fig. 20. Late anaphase in vegetative division. The chromatin of the chromo- 

 somes is reforming into large karyosomes. The daughter-spheres are beginning 

 to expand and to lose their densely granular appearance, while the characteristic 

 hyaline portion of the central part is plainly indicated, resembling the sphere in 

 Fig. I. 



Fig. 21. Late telophase and beginning of the secondary divisions. The 

 daughter-spheres have formed amphiasters, although the parent nucleus is not 

 completely divided as shown by the large " Verbindungsstiick." 



Fig. 22. Section of nuclear-plate stage showing nuclear plate and fan-like 

 ' arrangement of the chromosomes. 



Fig. 23. Late anaphase showing the collection of chromatin into karyosomes. 

 A centrosome (C) is plainly indicated at the focus of the mantle-fibers. There is 

 no nuclear membrane between chromosomes and sphere. 



Fig. 24. Similar anaphase showing aggregation of daughter-chromosomes 

 as in Fig. 18. No karyosome-formation taking place. Centrosome and mantle- 

 fibers present. 



Fig. 25. Late telophase in vegetative division. Remnants of the daughter- 

 chromosomes can still be made out, although most of the chromatin is now 

 collected in a number of karyosomes. 



